Method for fabricating wiring board provided with passive element, and wiring board provided with passive element

ABSTRACT

A fabricating method of a wiring board provided with passive elements is disclosed. The fabricating method includes coating one or both of resistive paste and dielectric paste on at least any one of first surfaces of a first metal foil and a second metal foil each of which has a first surface and a second surface; arranging an insulating board having thermo-plasticity and thermo-setting properties so as to face the first surface of the first metal foil, and arranging the first surface side of the second metal foil so as to face a surface different from a surface to which the first metal foil faces of the insulating board; forming a double-sided wiring board by stacking, pressurizing and heating the arranged first metal foil, insulating board, and second metal foil, and thereby integrating these; and patterning the first metal foil and/or the second metal foil.

This is a divisional application of U.S. patent application Ser. No.11/023,499, filed Dec. 29, 2004, now U.S. Pat. No. 7,100,276 which is adivision of application Ser. No. 10/160,179, filed Jun. 4, 2002, nowU.S. Pat. No. 6,872,893 which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for fabricating a wiring boardprovided with a passive element and to a wiring board provided with apassive element, in particular to a method for fabricating a wiringboard provided with a passive element having an aptitude for improvingcharacteristics of the passive element and to a wiring board providedwith a passive element having an aptitude for improving characteristicsof the passive element.

2. Description of the Related Art

As portable electronic devices become smaller in size, lighter in weightand thinner in thickness, smaller size chip components, such as L(inductor, coil), C (condenser, capacitor) and R (resistor), have beendeveloped. Furthermore, by burying passive elements such as C and L in awiring substrate, composite components have been developed. Suchintegration with a wiring substrate has been actively forwardedparticularly in multi-layered ceramic substrates and adopted in, forinstance, RF (radio frequency) modules for portable telephones.

A multi-layered ceramic substrate is fabricated by first preparing anecessary number of green sheets (ceramic material sheet beforesintering) on which coil patterns and capacitor electrode patterns areformed by, for instance, printing a thick film of a conductive paste,followed by stacking these in a predetermined order and by performingsimultaneous thermo-compression bonding and sintering.

Furthermore, a plurality of green sheets having different dielectricconstants is prepared, and according to characteristics of a passivecomponent to be incorporated, the green sheets are appropriatelyselected. This is performed by selecting a low dielectric constant greensheet that can set a high self-resonant frequency and secure a highQ-value for a ceramic material that constitutes an inductor, and a highdielectric constant green sheet for a ceramic layer that forms acapacitor, respectively. By use of such a combination, an LC compositecomponent having higher function may be incorporated.

In the aforementioned technique, ceramics is used for wiring substratematerial. It is expected that in future an operating frequency of an RFcircuit that is used in a portable telephone may reach 10 to 20 GHz. Inview of this, it is important from a viewpoint of product costs and soon that organic resins having lower relative dielectric constants aremade available as the substrate material. As things are, when an organicresin that is lower in dielectric constant than the ceramics is used asa substrate material (inter-layer insulating layer), and passiveelements such as capacitors and so on are incorporated similarly to themultilayer ceramic substrate, it is supposed that an element area maybecome larger and desired characteristics may not be obtained.

Furthermore, as to the so-called hybrid multi-layered substrates, thereare the following reports. That is, first, according to characteristicsof a passive element to be incorporated, a substrate material in which adielectric material and a magnetic material are mingled with polymer isprepared. Thus obtained substrate material is etched, and thereby apatterned capacitor layer and a coil layer are formed. These arelaminated in a predetermined order, and thereby a hybrid multi-layeredsubstrate is obtained.

However, in this technique, the multi-layered substrate may warp due tothe difference of characteristics such as thermal expansion coefficientand so on between the substrate materials. In addition, since only onespecified kind of passive element may be formed in one layer, a designallowance when the passive elements are arranged is low. That is, it isinappropriate in obtaining a smaller size due to tendency to an increasein the number of layers as a whole.

Furthermore, there is another multi-layered organic resin substrate inwhich resistive paste, dielectric paste, and conductive paste aresequentially printed to incorporate R, L and C. However, since the pastethat can be used in this case is restricted to kinds that allowcompleting heat treatment at temperatures lower than the heat resistancetemperature of an organic resin that is used as an insulating layer, thedesired characteristics may not be obtained in some cases.

SUMMARY OF THE INVENTION

The present invention is carried out in consideration of theaforementioned situations. That is, the present invention provides amethod for fabricating a wiring board that is provided with passiveelements having improved characteristics, and a wiring board that isprovided with such passive elements.

A method for fabricating a wiring board provided with a passive elementaccording to the present invention includes coating a resistive pasteand/or a dielectric paste on at least any one of first surfaces of afirst metal foil and a second metal foil each of which has the firstsurface and a second surface; arranging an insulating board havingthermo-plasticity and thermo-setting properties so as to face the firstsurface of the first metal foil, and arranging the first surface side ofthe second metal foil so as to face a surface different from a surfaceto which the first metal foil faces of the insulating board; forming adouble-sided wiring board by stacking, pressurizing and heating three,that is, the arranged first metal foil, insulating board, and secondmetal foil and thereby integrating these; and patterning the first metalfoil and/or the second metal foil of the formed double-sided wiringboard.

That is, resistive paste and dielectric paste are coated on a metalfoil. Accordingly, these pastes can be heat-treated (such as, forinstance, drying, sintering, and curing) irrespective of the heatresistance temperature of an insulating board. Thereafter, the metalfoil having thus, for instance, heat-treated resistive element anddielectrics and the insulating board are laminated. Accordingly, awiring board provided with passive elements having excellentcharacteristics can be obtained.

Furthermore, another method for fabricating a wiring board provided witha passive element according to the present invention includes coating aresistive paste on a first surface of at least a first metal foil of thefirst metal foil and a second metal foil each of which has the firstsurface and a second surface; forming a substantially conical conductivebump on a resistive element formed of the coated resistive paste;arranging an insulating board having thermo-plasticity and thermosettingproperties so as to face the first surface of the first metal foil, andarranging the first surface of the second metal foil so as to face asurface different from a surface to which the first metal foil faces ofthe insulating board; forming a double-sided wiring board by stacking,pressurizing and heating three, that is, the arranged first metal foil,insulating board, and second metal foil and thereby integrating these sothat the formed conductive bump may penetrate through the insulatingboard and establish an electrical contact and/or a heat conductivecontact with the second metal foil; and patterning the first metal foiland the second metal foil of the formed double-sided wiring board.

That is, a resistive paste is coated on a metal foil. Accordingly, theheat-treatment (such as, for instance, drying, sintering, and curing)and so on of the paste can be performed irrespective of the heatresistance temperature of an insulating board. Thereafter, the metalfoil having thus, for instance, heat-treated paste (resistive element)and the insulating board are laminated. Accordingly, a wiring boardprovided with passive elements (resistors in this case) having excellentcharacteristics can be obtained.

Furthermore, in this case, the wiring board may be configured so thatthe conductive bump may directly establish one or both of an electricalcontact and a heat conductive contact with the coated/formed resistiveelement. Accordingly, since a lead wire can be pulled out of theresistive element while avoiding a contact between the resistive elementand the metal foil, the resistive paste that is less compatible with ametal (for instance, copper) that is used for the metal foil may beused. Accordingly, by further expanding a range of choice of availableresistive pastes, a wiring board provided with a passive element havingexcellent characteristics may be obtained. Furthermore, when theconductive bump is brought into a heat conductive contact with theresistive element, for instance, a heat sink may be disposed on a rearsurface side (an opposite side from a surface side having a resistorthereon) of the insulating board.

Still furthermore, still another method for fabricating a wiring boardprovided with a passive element according to the present inventionincludes coating a dielectric paste on a first surface of at least asecond metal foil of a first metal foil and the second metal foil eachof which has the first surface and a second surface; coating aconductive paste so as to include on the coated dielectric paste andextend onto the first surface on which the dielectric paste is coated;arranging an insulating board having thermo-plasticity and thermosettingproperties so as to face the first surface of the first metal foil, andarranging the first surface of the second metal foil so as to face asurface different from a surface to which the first metal foil faces ofthe insulating board; forming a double-sided wiring board by stacking,pressurizing and heating three, that is, the arranged first metal foil,insulating board, and second metal foil and thereby integrating these;and patterning at least the second metal foil of the formed double-sidedwiring board.

That is, a dielectric paste is coated on a metal foil. Accordingly,heat-treatment (such as, for instance, drying, sintering, and curing)and so on of the paste can be performed irrespective of the heatresistance temperature of an insulating board. Thereafter, the metalfoil having thus, for instance, heat-treated paste (dielectric material)and the insulating board are laminated. Accordingly, a wiring boardprovided with a passive element (capacitor in this case) havingexcellent characteristics can be obtained.

Furthermore, in this case, furthermore, an electrical conductor formedof the conductive paste and the metal foil may sandwich dielectrics,thereby a so-called parallel plate capacitor is formed. Thereby, acapacitor having higher capacitance may be formed.

Still furthermore, still another method for fabricating a wiring boardprovided with a passive element according to the present inventionincludes coating a dielectric paste on a first surface of at least asecond metal foil of a first metal foil and the second metal foil eachof which has the first surface and a second surface; coating a firstconductive paste so as to contain on the coated dielectric paste and toextend onto the first surface on which the dielectric paste is coated;coating a second dielectric paste so as to contain on the coated firstconductive paste; coating a second conductive paste so as to contain onthe coated second dielectric paste, to extend onto the first surface onwhich the second dielectric paste is coated, and not to come intocontact with the first conductive paste; arranging an insulating boardhaving thermo-plasticity and thermosetting properties so as to face thefirst surface of the first metal foil, and arranging the first surfaceof the second metal foil so as to face a surface different from asurface to which the first metal foil faces of the insulating board;forming a double-sided wiring board by stacking, pressurizing andheating three, that is, the arranged first metal foil, insulating board,and second metal foil, and thereby integrating these; and patterning atleast the second metal foil of the formed double-sided wiring board.

That is, a dielectric paste and a conductive paste are coated on a metalfoil. Thereby, heat treatment (for instance, drying, sintering, andcuring) of the pastes may be performed irrespective of the heatresistance temperature of an insulating board. Since the metal foilhaving thus, for instance, heat-treated paste (dielectric material) islaminated together with the insulating board, a wiring board providedwith a passive element (capacitor in this case) excellent incharacteristics can be obtained.

In this case, furthermore, since an electrical conductor made of theconductive paste and the metal foil may be formed to sandwich thedielectrics, and the electrical conductor and an electrical conductormade of the second conductive paste may be formed to sandwich the seconddielectrics, a so-called parallel plate capacitor may be formed inmulti-layers. Thereby, a capacitor having higher capacitance may beformed. Such a multi-layered capacitor, by forming dielectrics and anelectrical conductor in a further multi-layered structure due to thedielectric paste and conductive paste, may be provided with furthermorehigher capacitance.

Furthermore, still another method for fabricating a wiring boardprovided with a passive element according to the present inventionincludes forming a substantially conical conductive bump on a firstsurface of a first metal foil having the first surface and a secondsurface; forming a substantially conical magnetically permeable bump ona first surface of a second metal foil having the first surface and asecond surface; arranging an insulating board having thermo-plasticityand thermosetting properties so as to face the first surface of thefirst metal foil, and arranging the first surface side of the secondmetal foil so as to face a surface different from a surface to which thefirst metal foil faces of the insulating board; forming a double-sidedwiring board by stacking, pressurizing and heating three, that is, thearranged first metal foil, insulating board, and second metal foil, andthereby integrating these so that the formed conductive bump andmagnetically permeable bump may penetrate through the insulating boardand establish a contact with the first or second metal foil; andpatterning the first metal foil and the second metal foil of the formeddouble-sided wiring board.

That is, a conductive bump and a magnetically permeable bump are formedon a metal foil. Accordingly, the bumps can be heat-treated (such as,for instance, drying, sintering, and curing) irrespective of the heatresistance temperature of an insulating board. Thereafter, the metalfoil having thus, for instance, heat-treated bump and the insulatingboard are laminated. Accordingly, a wiring board provided with a passiveelement (in this case inductor) having excellent characteristics may beobtained.

Furthermore, in this case, furthermore, due to patterning of a first andsecond metal layers and due to an electrical connection between these bymeans of a conductive bump, a helical inductor with the magneticallypermeable bump as a core may be formed. Accordingly, ones having largerinductance may be formed.

A wiring board provided with a passive element according to the presentinvention includes an insulating board having a first surface and asecond surface; a layered resistive element and/or a layered dielectricsdisposed on the first surface and/or the second surface of theinsulating board so as to sink in a thickness direction of theinsulating board; and a first wiring layer and a second wiring layerthat are, respectively, disposed on the first surface and the secondsurface of the insulating board, and each of which has a connection withthe layered resistive element/the layered dielectrics disposed on thecorresponding first surface/second surface.

Furthermore, another wiring board provided with a passive elementaccording to the present invention includes an insulating board having afirst surface and a second surface; a layered resistive element disposedon the second surface of the insulating board so as to sink in athickness direction of the insulating board; a first and second wiringlayers disposed on the first surface and second surface of theinsulating board, respectively; and a conductive bump that penetratesthrough the insulating board and is in an electrical connection and/or aheat conductive connection with the layered resistive element and thefirst wiring layer.

Still furthermore, still another wiring board provided with a passiveelement according to the present invention includes an insulating boardhaving a first surface and a second surface; a layered electricalconductor disposed on the second surface of the insulating board so asto sink in a thickness direction of the insulating board; a layereddielectrics disposed in partial contact with a top surface of thelayered electrical conductor so as to sink in a thickness direction ofthe insulating board; and a wiring layer that is disposed on the secondsurface of the insulating board and has individual connections with thelayered electrical conductor and the layered dielectrics.

Furthermore, still another wiring board provided with a passive elementaccording to the present invention includes an insulating board having afirst surface and a second surface; a first and second wiring layers,respectively, disposed on the first surface and the second surface ofthe insulating board; a conductive bump that penetrates through theinsulating board and is in an electrical connection with the firstwiring layer and the second wiring layer; and a magnetically permeablebump that penetrates through the insulating board. In the above, thefirst wiring layer has a first pattern that surrounds the magneticallypermeable bump, the second wiring layer has a second pattern thatsurrounds the magnetically permeable bump, and the first and secondpatterns are in an electrical continuity due to the conductive bump.

The wiring boards are ones that can be fabricated by the aforementionedrespective fabricating methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the drawings, which arepresented for the purpose of illustration only and do not limit thescope of the invention.

FIG. 1A and FIG. 1B are diagrams showing a process for fabricating adouble-sided wiring board according to a fabricating method according toan embodiment of the present invention.

FIG. 2A and FIG. 2B are diagrams showing a process for fabricating adouble-sided wiring board according to a fabricating method according toanother embodiment of the present invention.

FIG. 3 is a perspective view showing an example of the double-sidedwiring board fabricated by the process shown in FIG. 1A and FIG. 1B, orFIG. 2A and FIG. 2B.

FIG. 4A and FIG. 4B are diagrams showing a process for making thedouble-sided wiring board that is fabricated by the process shown inFIG. 1A and FIG. 1B, or FIG. 2A and FIG. 2B into a material of athree-layered or four-layered material.

FIG. 5A and FIG. 5B are diagrams showing a metal foil necessary when thethree-layered wiring board or four-layered wiring board is fabricated byuse of the double-sided wiring board that is fabricated by the processshown in FIG. 1A and FIG. 1B, or FIG. 2A and FIG. 2B, and a processapplied thereon.

FIG. 6 includes diagrams showing a process for fabricating thefour-layered wiring board by use of a wiring board material that isfabricated by the process shown in FIG. 4A and FIG. 4B, and the metalfoil shown in FIG. 5A and FIG. 5B.

FIG. 7 includes perspective views showing the process shown in FIG. 6.

FIG. 8 is a perspective view showing the four-layered wiring boardfabricated according to the fabricating method shown in FIG. 6 (FIG. 7)and having a loop antenna in an outer wiring.

FIG. 9 is a partial sectional view as an example of a double-sidedwiring board fabricated according to the fabricating method according tostill another embodiment of the present invention.

FIG. 10 is a bottom view of the double-sided wiring board shown in FIG.9.

FIG. 11 is a partial sectional view showing another example to theexample shown in FIG. 9.

FIG. 12A and FIG. 12B are partial sectional views for explaining anexample of a double-sided wiring board fabricated according to thefabricating method according to still another embodiment of the presentinvention.

FIG. 13A and FIG. 13B are partial sectional views for explaining anotherexample to the example shown in FIG. 12A and FIG. 12B.

FIG. 14A and FIG. 14B are diagrams for explaining irregularity in theshape at a periphery of the dielectrics/resistive element/electricalconductor coated on the metal foil and an improvement thereof.

FIG. 15A and FIG. 15B are diagrams for explaining an example of afour-layered wiring board fabricated according to the fabricating methodaccording to still another embodiment of the present invention.

FIG. 16A and FIG. 16B are diagrams for explaining another example to theexample shown in FIG. 15A and FIG. 15B.

DETAILED DESCRIPTION OF THE INVENTION

The fabricating method according to the present invention, as animplementation mode, further includes forming a substantially conicalconductive bump on the first surface of the first metal foil. In thiscase, the forming a double-sided wiring board is performed so that theformed conductive bump may penetrate through the insulating board andestablish an electrical contact with the second metal foil. That is,since wiring layers on both sides are electrically connected by means ofa conductive bump, the number of the processes may be reduced and adouble-sided wiring board whose wiring layers on both sides have anelectrical continuity may be easily fabricated.

Furthermore, in an implementation mode of the fabricating methodaccording to the present invention, the patterning the first metal foiland/or the second metal foil includes the formation of an inductor thatis vertically formed due to a pattern and/or a loop antenna that isformed loop-like due to a pattern. That is, an inductor and a loopantenna are formed by patterning a metal foil.

Still furthermore, the fabricating method according to the presentinvention further includes trimming a resistor formed from the resistivepaste by use of the patterned first metal foil and/or the patternedsecond metal foil as an electrode. That is, since an electrode can beformed to a resistor due to the patterning, by making use thereof forresistance measurement, is the resistor trimmed.

Furthermore, in an implementation mode of the fabricating methodaccording to the present invention, the coating the resistive pasteand/or the dielectric paste includes removing a periphery portionthereof after the coating. By removing irregularity at the edge portionsof the coated resistive element and dielectrics, the resistor andcapacitor having higher accuracy may be obtained.

Still furthermore, the fabricating method according to the presentinvention, as an implementation mode, further includes forming asubstantially conical conductive bump on a first surface of a thirdmetal foil having the first surface and a second surface; arranging asecond insulating board having thermo-plasticity and thermosettingproperties so as to face the first surface of the third metal foil, andarranging the first metal foil side of the double-sided wiring board soas to face a surface different from a surface that faces the third metalfoil of the second insulating board; forming a three-layered wiringboard by stacking, pressurizing and heating three, that is, the arrangedthird metal foil, second insulating board, and double-sided wiringboard, and thereby integrating these so that the conductive bump formedon the third metal foil may penetrate through the second insulatingboard and establish an electrical contact with the first metal foil; andpatterning the third metal foil of the formed three-layered wiringboard.

That is, by use of a double-sided wiring board as a material, and byfurther establishing an interlayer connection with a third wiring layerdue to a conductive bump, a three-layered wiring board is fabricated.

Still furthermore, the fabricating method according to the presentinvention, as an implementation mode, further includes coating aresistive paste and/or a dielectric paste on a first surface of a thirdmetal foil having the first surface and a second surface; forming asubstantially conical conductive bump on the first surface of the thirdmetal foil; arranging a second insulating board having thermo-plasticityand thermosetting properties so as to face the first surface of thethird metal foil, and arranging a first metal foil side of thedouble-sided wiring board so as to face a surface different from asurface that faces the third metal foil of the second insulating board;forming a three-layered wiring board by stacking, pressurizing andheating three, that is, the arranged third metal foil, second insulatingboard, and double-sided wiring board, and thereby integrating these sothat the conductive bump formed on the third metal foil may penetratethrough the second insulating board and establish an electrical contactwith the first metal foil; and patterning the third metal foil of theformed three-layered wiring board.

That is, by use of a double-sided wiring board as a material, by furtherestablishing an interlayer connection with a third wiring layer due to aconductive bump, a three-layered wiring board is fabricated. Here, apassive element may be enabled to use in the third wiring layer.

Furthermore, the fabricating method according to the present invention,as an implementation mode, further includes forming a substantiallyconical conductive bump on the second surface of the second metal foilof the formed double-sided wiring board; arranging a second insulatingboard having thermo-plasticity and thermosetting properties so as toface a side on which the conductive bump of the double-sided wiringboard is formed, and arranging a third metal foil so as to face asurface different from a surface that faces the double-sided wiringboard of the second insulating board; forming a three-layered wiringboard by stacking, pressurizing and heating three, that is, the arrangeddouble-sided wiring board, second insulating board, and third metalfoil, and thereby integrating these so that the conductive bump formedon the double-sided wiring board may penetrate through the secondinsulating board and establish an electrical contact with the thirdmetal foil; and patterning the third metal foil of the formedthree-layered wiring board.

Also in this case, with a double-sided wiring board as a material, byfurther use of a conductive bump, an interlayer connection with a thirdwiring board is established, thereby forming a three-layered wiringboard.

Still furthermore, the fabricating method according to the presentinvention, as an implementation mode, further includes coating aresistive paste and/or a dielectric paste on a first surface of a thirdmetal foil having the first surface and a second surface; forming asubstantially conical conductive bump on the second surface of thesecond metal foil of the formed double-sided wiring board; arranging asecond insulating board having thermo-plasticity and thermosettingproperties so as to face a side on which the conductive bump of thedouble-sided wiring board is formed, and arranging the first surfaceside of the third metal foil so as to face a surface different from asurface that faces the double-sided wiring board of the secondinsulating board; forming a three-layered wiring board by stacking,pressurizing and heating three, that is, the arranged double-sidedwiring board, second insulating board, and third metal foil, and therebyintegrating these so that the conductive bump formed on the double-sidedwiring board may penetrate through the second insulating board andestablish an electrical contact with the third metal foil; andpatterning the third metal foil of the formed three-layered wiringboard.

In this case too, by use of a double-sided wiring board as a material,by further establishing an interlayer connection with a third wiringlayer due to a conductive bump, a three-layered wiring board isfabricated. Here, a passive element may be enabled to use in the thirdwiring layer.

Furthermore, in an implementation mode of the fabricating methodaccording to the present invention, the patterning the third metal foilincludes the formation an inductor that is vertically formed due to apattern and/or a loop antenna that is formed loop-like due to a pattern.That is, by patterning the third metal foil, an inductor and a loopantenna may be formed.

Still furthermore, in an implementation mode of the fabricating methodof the present invention, the coating a resistive paste and/or adielectric paste on the first surface of the third metal foil includesremoving a periphery portion thereof after the coating. This is aprocess to obtain a resistive element and dielectrics having higheraccuracy from a resistive paste and dielectric paste coated on a thirdmetal foil.

Furthermore, the fabricating method according to the present invention,as an implementation mode, further includes forming a substantiallyconical conductive bump on a first surface of a third metal foil havingthe first surface and a second surface; forming a substantially conicalsecond conductive bump on the second surface of the second metal foil ofthe formed double-sided wiring board; arranging a second insulatingboard having thermo-plasticity and thermosetting properties so as toface the first surface of the third metal foil, arranging the firstmetal foil side of the double-sided wiring board so as to face a surfacedifferent from a surface to which the third metal foil faces of thesecond insulating board, arranging a third insulating board havingthermo-plasticity and thermosetting properties so as to face a side onwhich the second conductive bump is formed of the double-sided wiringboard, and arranging the fourth metal foil so as to face a surfacedifferent from a surface that faces the double-sided wiring board of thethird insulating board; forming a four-layered wiring board by stacking,pressurizing and heating five, that is, the arranged third metal foil,second insulating board, double-sided wiring board, third insulatingboard, and fourth metal foil, and thereby integrating these so that theconductive bump formed on the third metal foil may penetrate through thesecond insulating board and establish an electrical contact with thefirst metal foil and the second conductive bump formed on thedouble-sided wiring board may penetrate through the third insulatingboard and establish an electrical contact with the fourth metal foil;and patterning the third metal foil and/or the fourth metal foil of theformed four-layered wiring board.

That is, by use of a double-sided wiring board as a material, byestablishing an interlayer connection between the third and fourthwiring layers due to a conductive bump, a four-layered wiring board isfabricated.

Still furthermore, the fabricating method according to the presentinvention, as an implementation mode, further includes coating aresistive paste and/or a dielectric paste on at least any one of firstsurfaces of a third and fourth metal foils each of which has the firstsurface and a second surface; forming a substantially conical conductivebump on the first surface of the third metal foil; forming asubstantially conical second conductive bump on the second surface ofthe second metal foil of the formed double-sided wiring board; arranginga second insulating board having thermo-plasticity and thermosettingproperties so as to face the first surface of the third metal foil,arranging the first metal foil side of the double-sided wiring board soas to face a surface different from a surface to which the third metalfoil faces of the second insulating board, arranging a third insulatingboard having thermo-plasticity and thermosetting properties so as toface a side on which the second conductive bump is formed of thedouble-sided wiring board, and arranging the first surface side of thefourth metal foil so as to face a surface different from a surface thatfaces the double-sided wiring board of the third insulating board;forming a four-layered wiring board by stacking, pressurizing andheating five, that is, the arranged third metal foil, second insulatingboard, double-sided wiring board, third insulating board, and fourthmetal foil, and thereby integrating these so that the conductive bumpformed on the third metal foil may penetrate through the secondinsulating board and establish an electrical contact with the firstmetal foil and the second conductive bump formed on the double-sidedwiring board may penetrate through the third insulating board andestablish an electrical contact with the fourth metal foil; andpatterning the third metal foil and/or the fourth metal foil of theformed four-layered wiring board.

Also in this case, by use of a double-sided wiring board as a material,by further establishing an interlayer connection with a third and fourthwiring layer due to a conductive bump, a four-layered wiring board isfabricated. Even in the third and fourth wiring-layers, passive elementsmay be utilized.

Furthermore, in an implementation mode of the fabricating methodaccording to the present invention, the patterning the third metal foiland/or the fourth metal foil includes the formation of an inductor thatis vortically formed due to a pattern and/or a loop antenna that isformed loop-like due to a pattern. That is, by patterning a third metalfoil and a fourth metal foil, an inductor and a loop antenna may beformed.

Still furthermore, in an implementation mode of the fabricating methodof the present invention, the coating a resistive paste and/or adielectric paste on at least any one of the first surfaces of the thirdand fourth metal foils includes removing a periphery portion thereofafter the coating. This is a process for obtaining a resistive elementand/or dielectrics having higher accuracy from the resistive paste andthe dielectric paste coated on the third metal foil and/or the fourthmetal foil.

Furthermore, the fabricating method according to the present invention,as an implementation mode, further includes forming a substantiallyconical second conductive bump on a first surface of a third metal foilhaving the first surface and a second surface; forming a substantiallyconical second magnetically permeable bump on a first surface of afourth metal foil having the first surface and a second surface; forminga substantially conical third conductive bump on the second surface ofthe second metal foil of the formed double-sided wiring board; forming asubstantially conical third magnetically permeable bump on a surface ofthe first metal foil side of the formed double-sided wiring board;arranging a second insulating board having thermo-plasticity andthermosetting properties so as to face the first surface of the thirdmetal foil, arranging a first metal foil side of the double-sided wiringboard so as to face a surface different from a surface to which thethird metal foil faces of the second insulating board, arranging a thirdinsulating board having thermo-plasticity and thermosetting propertiesso as to face a side on which the third conductive bump is formed of thedouble-sided wiring board, and arranging the first surface side of afourth metal foil so as to face a surface different from a surface thatfaces the double-sided wiring board of the third insulating board;forming a four-layered wiring board by stacking, pressurizing andheating five, that is, the arranged third metal foil, second insulatingboard, double-sided wiring board, third insulating board, and a fourthmetal foil, and thereby integrating these so that the second conductivebump formed on the third metal foil may penetrate through the secondinsulating board and establish an electrical contact with the firstmetal foil, the second magnetically permeable bump formed on thedouble-sided wiring board may penetrate through the second insulatingboard and establish a contact with the third metal foil, the thirdconductive bump formed on the double-sided wiring board may penetratethrough the third insulating board and establish an electrical contactwith the fourth metal foil, and the third magnetically permeable bumpformed on the fourth metal foil may penetrate through the thirdinsulating board and establish a contact with a surface of the secondmetal foil side of the double-sided wiring board; and patterning thethird metal foil and the fourth metal foil of the formed four-layeredwiring board.

That is, by use of a magnetically permeable bump as a core, a helicalinductor is attempted to form in the four-layered wiring board.

Furthermore, the fabricating method according to the present invention,as an implementation mode, further includes forming a through-hole in aformed double-sided wiring board and filling a magnetically permeablematerial in the formed through-hole. In place of the magneticallypermeable bump, a pillar-like body formed by filling a magneticallypermeable material in a through-hole may be used as a core of a helicalinductor.

Furthermore, the fabricating method according to the present inventionis a fabricating method of a wiring board provided with a passiveelement that, as an implementation mode, further includes forming asubstantially conical conductive bump on the first surface of the firstmetal foil, and the forming a double-sided wiring board is performed sothat the formed conductive bump may penetrate through the insulatingboard and establish an electrical contact with the second metal foil.The present fabricating method further includes forming a substantiallyconical second conductive bump on a first surface of a third metal foilhaving the first surface and a second surface; forming a substantiallyconical third conductive bump on the second surface of the second metalfoil of the formed double-sided wiring board; arranging a secondinsulating board having thermo-plasticity and thermosetting propertiesso as to face the first surface of the third metal foil, arranging thefirst metal foil side of the double-sided wiring board so as to face asurface different from a surface to which the third metal foil faces ofthe second insulating board, arranging a third insulating board havingthermo-plasticity and thermosetting properties so as to face a side onwhich the third conductive bump is formed of the double-sided wiringboard, and arranging the fourth metal foil so as to face a surfacedifferent from a surface that faces the double-sided wiring board of thethird insulating board; forming a four-layered wiring board by stacking,pressurizing and heating five, that is, the arranged third metal foil,second insulating board, double-sided wiring board, third insulatingboard, and fourth metal foil, and thereby integrating these so that thesecond conductive bump formed on the third metal foil may penetratethrough the second insulating board and establish an electrical contactwith the first metal foil and the third conductive bump formed on thedouble-sided wiring board may penetrate through the third insulatingboard and establish an electrical contact with the fourth metal foil;patterning the third metal foil and the fourth metal foil of the formedfour-layered wiring board; forming a through-hole in the formedfour-layered wiring board; and filling a magnetically permeable materialin the formed through-hole.

In this case too, in place of the magnetically permeable bump, apillar-like body that is formed by filling a magnetically permeablematerial in a through-hole is attempted to use as a core of a helicalinductor. The wiring board has a four-layered wiring layer.

Furthermore, the wiring board according to the present invention, as animplementation mode, further includes a conductive bump that penetratesthrough the insulating board, wherein each of the first and secondwiring layers has an electrical connection with the conductive bump.That is, since the electrical connection between the wiring layers onboth sides is performed by use of a conductive bump, the present wiringboard is a wiring board whose both wiring layers have an electricalcontinuity and enables to reduce the number of processes, that is, torealize higher productivity.

Furthermore, as an implementation mode of the wiring board according tothe present invention, at least one of the first and second wiringlayers has an inductor that is vortically formed due to a pattern and/ora loop antenna that is formed loop-like due to a pattern. That is, aninductor and a loop antenna are formed as a metal foil pattern.

Still furthermore, a wiring board according to the present invention, asan implementation mode, further includes a second insulating boarddisposed in contact with the first wiring layer side of the insulatingboard; a conductive bump that penetrates through the second insulatingboard; and a third wiring layer disposed on a side different from theinsulating board side of the second insulating board; wherein the firstwiring layer of the insulating board is disposed so as to sink in athickness direction of the second insulating board; and each of thefirst and third wiring layers has an electrical connection with theconductive bump. This is a three-layered wiring board that contains adouble-sided wiring board inside thereof and in which an interlayerconnection with a third wiring layer is established by means of aconductive bump.

Still furthermore, a wiring board according to the present invention, asan implementation mode, further includes a second layered resistiveelement and/or a second layered dielectrics disposed on the third wiringlayer side of the second insulating board so as to sink in a thicknessdirection of the second insulating board; wherein the third wiring layerhas a connection with the second layered resistive element/the secondlayered dielectrics. Thereby, a passive element is made available evenin a third wiring layer.

Furthermore, as an implementation mode of a wiring board according tothe present invention, the third wiring layer has an inductor that isvortically formed due to a pattern and/or a loop antenna that is formedloop-like due to a pattern. That is, an inductor and a loop antenna areformed as a metal foil pattern.

Still furthermore, a wiring board according to the present inventionfurther includes, as an implementation mode, a third insulating boarddisposed in contact with the second wiring layer side of the insulatingboard; a second conductive bump that penetrates through the thirdinsulating board; and a fourth wiring layer disposed on a side differentfrom the insulating board side of the third insulating board; whereinthe second wiring layer of the insulating board is disposed so as tosink in a thickness direction of the third insulating board; and each ofthe second and fourth wiring layers has an electrical connection withthe second conductive bump. This is a four-layered wiring board thatcontains a double-sided wiring board as a core wiring board and in whichinterlayer connections with third and fourth wiring layers are furtherimplemented by means of conductive bumps.

Still furthermore, a wiring board according to the present inventionfurther includes, as an implementation mode, a second layered resistiveelement and/or a second layered dielectrics disposed on the fourthwiring layer side of the third insulating board so as to sink in athickness direction of the third insulating board; wherein the fourthwiring layer has a connection with the second layered resistiveelement/the second layered dielectrics. Thereby, a passive element ismade available even in third and fourth wiring layers.

Furthermore, as an implementation mode of a wiring board according tothe present invention, the fourth wiring layer has an inductor that isvortically formed due to a pattern and/or a loop antenna that is formedloop-like due to a pattern. That is, an inductor and a loop antenna areformed as a metal foil pattern.

Still furthermore, a wiring board according to the present inventionfurther includes, as an implementation mode, a second layereddielectrics disposed under a bottom surface of the layered electricalconductor and a second electrical conductor that is disposed includingunder the bottom surface of the second layered dielectrics and isbrought into contact with the wiring layer. That is, the present wiringboard includes a multi-layered parallel plate capacitor.

Furthermore, a wiring board according to the present invention, as animplementation mode, further includes a second insulating board disposedon the first wiring layer side of the insulating board; a thirdinsulating board disposed on the second wiring layer side of theinsulating board; a third wiring layer disposed on a different surfaceside from the insulating board of the second insulating board; a fourthwiring layer disposed on a different surface side from the insulatingboard of the third insulating board; a second conductive bump thatpenetrates through the second insulating board and is brought intoelectrical connections with the first wiring layer and the third wiringlayer; a second magnetically permeable bump that penetrates through thesecond insulating board; a third conductive bump that penetrates throughthe third insulating board and is brought into electrical connectionswith the second wiring layer and the fourth wiring layer; and a thirdmagnetically permeable bump that penetrates through the third insulatingboard; wherein the first wiring layer is disposed so as to sink in athickness direction of the second insulating board; the second wiringlayer is disposed so as to sink in a thickness direction of the thirdinsulating board; the magnetically permeable bump, the secondmagnetically permeable bump and the third magnetically permeable bumpare disposed in series; the third wiring layer has a third pattern thatsurrounds the second magnetically permeable bump; the fourth wiringlayer has a fourth pattern that surrounds the third magneticallypermeable bump; the first and third patterns are in an electricalcontinuity due to the second conductive bump; and the second and fourthpatterns are in an electrical continuity due to the third conductivebump.

That is, by use of a magnetically permeable bump as a core, a helicalinductance is formed in a four-layered wiring board.

Furthermore, a wiring board according to the present invention includes,as an implementation mode, in place of the magnetically permeable bump,the second magnetically permeable bump, and the third magneticallypermeable bump, a pillared body that has a magnetically permeablematerial and penetrates through the insulating board, the secondinsulating board, and the third insulating board. That is, in place of amagnetically permeable bump as a core, a pillar having a magneticallypermeable material is used as a core of a helical inductor.

In the following, embodiments of the present invention will be explainedwith reference to the drawings. FIG. 1A and FIG. 1B are diagrams showinga process for fabricating a double-sided wiring board according to oneembodiment of the present invention.

First, as shown in FIG. 1A upper side, a metal foil (a copper foil, forinstance) 1 is prepared. On this metal foil 1, a dielectric paste iscoated to be dielectrics 2 of a passive element (capacitor) necessary asa wiring board. Although a coating method is not particularlyrestricted, when, for instance, a screen-printing is used, over anentire surface, as many as necessary may be coated with highproductivity and relatively high accuracy. As a dielectric paste, forinstance, a composite in which powder of barium titanate, a highdielectric material is dispersed in a resinous binder may be used. As anexample, a dielectric paste CX-16, which is commercially available fromASAHI Kagaku Kenkyusho, may be utilized.

Furthermore, on the metal foil 1, a resistive paste is coated to be aresistive element 3 of a passive element (resistor) necessary as awiring board. The coating method of the resistive paste is alsoidentical as that mentioned above. As a resistive paste, for instance, acomposite in which resistive material powder is dispersed in a resinousbinder may be used. As an example, resistive pastes TU-15-8, TU-50-8, orTU-100-8, which are commercially available from ASAHI Kagaku Kenkyusho,may be utilized.

It is generally better to separately coat a dielectric paste and aresistive paste followed by separately drying and so on. It is becauseafter the drying, a former coating state, without being interfered, maybe maintained. The processing such as the drying and so on may beperformed, irrespective of a heat resistance temperature of aninsulating board (organic material) to be referred to later, attemperatures adequate for processing each of the dielectric paste andthe resistive paste. Accordingly, since a range of choice of kindsthereof is wide, it contributes in the formation of a passive elementhaving higher accuracy.

Furthermore, in order to make the resistive element 3 furthermoreaccurate, a method (post-treatment) as shown in FIG. 14A and FIG. 14Bmay be used. FIG. 14A and FIG. 14B are diagrams for explainingirregularity in the shape at a periphery portion of the resistiveelement (/dielectrics/electrical conductor) formed on a metal foil andan improvement thereof. FIG. 14A is a sectional view and FIG. 14B is atop view thereof.

In the resistive element 3 coated by means of the screen-printing and soon, in general, as shown in FIG. 14A, a shape, such as a thickness atthe periphery thereof is formed a little differently from that of aninside portion (edge effect). Such a thickness variation may causeirregularity in a sheet resistance value (one of characteristic value ofa resistive element; a resistance value between opposite sides of asquare). Accordingly, edge portions 30 of the resistive element 3 areremoved when the resistive element 3 is formed on the metal foil 1. Insuch removal, for instance, laser beam may be used. Since, due to suchthe removal, a thickness is more homogenized, a resistive element havinga resistance value closer to that expected from the sheet resistancevalue may be formed. In the case of the dielectrics 2, accuracy isobtained similarly.

As mentioned above, a coated and formed metal foil 4 on a surface ofwhich the resistive element 3 and the dielectrics 2 are formed isformed. Next, as shown in FIG. 1B upper side, resistive element3/dielectrics 2 sides of two coated and formed metal foils 4 arearranged at a predetermined position necessary as a wiring board so asto face both sides of a prepreg to be an insulating board 5. The prepregis obtained by impregnating a curable resin such as, for instance, epoxyresin in a reinforcing material such as glass fiber. Before curing, itis in a semi-cured state and has thermo-plasticity and thermo-settingproperties.

Next, as shown in FIG. 1B center, three, that is, the coated/formedmetal foil 4, insulating board 5 and another coated/formed metal foil 4are stacked, pressurized and heated and thereby integrating these, adouble-sided wiring board 6 is obtained. In the double-sided wiringboard 6, the dielectrics 2 and the resistive element 3 are integrated soas to sink in a thickness direction of the insulating board 5. This isdue to the thermo-plasticity and thermo-setting properties of theprepreg to be the insulating board 5.

Next, as shown in FIG. 1B lower side, the metal foils 1 on both sidesare patterned into patterns 1 a necessary as a wiring board. Due to thepatterning, a double-sided wiring board 7 on which at least both endelectrodes of the dielectrics 2 and the resistive element 3 are formedmay be obtained. In the patterning, existing methods such as, forinstance, the formation of a mask due to coating of photo-resist andexposure thereof, etching of the metal foil 1 due to the mask, and so onmay be used.

In addition, the resistive element 3 may be trimmed by use of the bothend electrodes formed by the patterning as resistance value measuringterminals. The trimming is a process in which, for instance, by use oflaser light, the resistive element 3 is partially burned and brought toconform to a predetermined resistance value.

Although processes following the above are not shown in the drawings,the formation of solder resist and plating layers including on thepattern 1 a, mounting of surface-mounting components on the pattern 1 a,or flip-chip mounting of semiconductor chips may be implementedaccording to existing methods. Furthermore, as well known, athrough-hole is bored in a double-sided wiring board 7, a conductivelayer is formed on an internal surface thereof, and thereby thedouble-sided wiring board 7 having an electrical continuity between bothwiring layers thereof may be formed. Still furthermore, according to theaforementioned etching of the metal foil 1, a vortical inductor may beformed. In this case, such a through-hole may be utilized as an insideterminal.

In the aforementioned embodiments, since materials are selected from awide range of choice and the dielectrics 2 and the resistive element 3are previously formed from the selected materials on the metal foil 1,on the same layer, a capacitor and resistor excellent in characteristicsmay be formed in a mingled state. Furthermore, since an organic materialis used as the insulating board 5, lighter weight may be realized thanin the case of ceramics.

In the aforementioned explanation, each of the dielectrics 2 to be acapacitor, and the resistive element 3 to be a resistor is formed bycoating a paste-like composite. However, other than this, when avortical inductor is formed, a conductive paste may be previously coatedvortically as a paste-like composite on a metal foil 1.

Next, a process for fabricating a double-sided wiring board according toa fabricating method according to another embodiment of the presentinvention will be explained with reference to FIG. 2A and FIG. 2B. FIG.2A and FIG. 2B are diagrams showing a process for fabricating adouble-sided wiring board according to a fabricating method according toanother embodiment of the present invention. The same regions as FIG. 1Aand FIG. 1B are given the same reference numerals. Explanation of thesame regions will be omitted.

This embodiment is different from one shown in FIG. 1A and FIG. 1B inthat as shown in FIG. 2A lower side, a process in which thecoated/formed metal foil 4 is transformed into a conductive bump formedmetal foil 4 a on which conductive bumps 8 have been formed is added.

The conductive bump 8 may be formed on a place necessary as a wiringboard on the coated/formed metal foil 4 a by means of, for instance,screen printing. For this, as a conductive paste, for instance, one thatis prepared by dispersing metal particles (silver, gold, copper, solderand so on) in a paste-like resin followed by mixing a volatile solventis coated on the metal foil 4 by means of screen printing. Theconductive bump 8 is necessary to have a height enough to penetratethrough the insulating board 5 as will be detailed later. Accordingly,when one time screen-printing cannot give a necessary height, byrepeating the screen-printing a plurality of times while disposing adrying process between the consecutive screen-printings, a height isincreased and thereby forming a substantially conical shape as a wholeis performed.

After the conductive bump formed metal foil 4 a is obtained as shown inthe above, next, as shown in FIG. 2B upper side, a resistive element 3and dielectrics 2 side of the coated/formed metal foil 4 is disposed soas to face one side of both sides of the prepreg to be a insulatingboard 5, and a resistive element 3, dielectrics 2 and conductive bump 8side of the conductive bump formed metal foil 4 a is disposed so as toface the other side of both sides of the prepreg.

Next, as shown in FIG. 2B center, a double-sided wiring board 6 a isobtained by stacking, pressurizing and heating three, that is, thecoated/formed metal foil 4, insulating board 5, and conductive bumpformed metal foil 4 a, and thereby integrating these. In thedouble-sided wiring board 6 a, the dielectrics 2 and resistive element 3are integrated so as to sink in a thickness direction of the insulatingboard 5, and the conductive bump 8 penetrates through the insulatingboard 5 and comes into an electrical contact with the opposing metalfoil 1. Such a state is realized because, as mentioned above, theinsulating board 5 had thermo-plasticity and thermo-setting properties,and the conductive bump 8 is originally formed into a substantial cone.

In the double-sided wiring board 6 a, since an electrical continuitybetween both wiring layers is established by the conductive bump 8,there is no need of a further process such as the formation of athrough-hole to establish an electrical continuity between both wiringlayers. Accordingly, since a space for the formation of the through-holeis not necessary, a wiring board of higher density may be obtained.Furthermore, in the integrating process, since a pressure on thedielectrics 2 and the resistive element 3 may be alleviated by theconductive bump 8 that works as a support, there is an advantageouseffect that dispersions of various characteristics of the dielectrics 2and the resistive element 3 that are caused at the integration may besuppressed.

Following the above, as shown in FIG. 2B lower side, the metal foils 1on both sides are patterned into a pattern 1 a necessary as a wiringboard (substantially similar to the case of FIG. 1B lower side). Due tothe patterning, a double-sided wiring board 7 a in which both endelectrodes of the dielectrics 2 and the resistive element 3 are at leastformed may be obtained. In addition to this, the resistive element 3 maybe trimmed by use of the both end electrodes formed by this patterningas resistance value measurement terminals. This is also as explainedabove.

Furthermore, although the processes following the above are not shown inthe drawings, the formation of solder resist and plating layersincluding on the pattern 1 a, mounting of surface-mounting components onthe pattern 1 a, or flip-chip mounting of semiconductor chips and so onmay be performed, according to existing methods. Still furthermore,according to the etching of the metal foil 1 as mentioned above, avortical inductor may be formed. In this case, the above-explainedconductive bump 8 may be utilized as an inside terminal.

In the above-explained embodiment, similarly to the embodiment explainedin FIG. 1A and FIG. 1B, since materials are selected from a large choiceof materials and the dielectrics 2 and the resistive element 3 areformed previously on the metal foil 1, a capacitor and resistorexcellent in characteristics may be incorporated in the same layer in amingled state. Furthermore, since an organic material is used as theinsulating board 5, lighter weight may be realized than in the case ofceramics. Furthermore, in order to form a vortical inductor, in advancethe conductive paste may be vertically coated on the metal foil 1.

FIG. 3 is a perspective view showing the double-sided wiring board 7that can be formed according to the embodiment explained in FIG. 1A andFIG. 1B, or the double-sided wiring board 7 a that can be formedaccording to the embodiment explained in FIG. 2A and FIG. 2B. As shownin FIG. 3, on both sides (one side may be allowed) of the insulatingboard 5, a resistor due to the resistive element 3, a capacitor due tothe dielectrics 2, and a vortical inductor due to the pattern 1 a may beincorporated in a state previously provided to the wiring boards 7/7 a.By making use of the wiring pattern 1 a as a land to mount surface mountcomponents and semiconductor devices on both sides of the double-sidedwiring board 7 a, it may be of course used as a mounted wiring board asit is.

FIG. 4A and FIG. 4B are diagrams showing a process carried out to makethe double-sided wiring board 7 a (7) that is fabricated according tothe process shown in FIG. 1A and FIG. 1B, or FIG. 2A and FIG. 2B amaterial of a four-layered wiring board. FIG. 4A is a sectional view,and FIG. 4B is a perspective view. FIG. 5A and FIG. 5B are diagramsshowing a necessary metal foil when a four-layered wiring board isfabricated with the double-sided wiring board 7 a (7) fabricatedaccording to the process shown in FIG. 1A and FIG. 1B, or FIG. 2A andFIG. 2B and a process applied thereon. FIG. 5A is a sectional view, andFIG. 5B is a perspective view. Furthermore, already explained regions inthese figures are given the same reference numerals. An N-layered wiringboard is a wiring board in which the number of the wiring layers is N.

First, as shown in FIG. 4A and FIG. 4B, in order to use the double-sidedwiring board 7 a (7) as a core wiring board, conductive bumps 9 areformed on necessary positions on one side thereof (positions accordingto a layout as a particular four-layered wiring board). The formation ofthe conductive bumps 9 may be implemented substantially similarly to thealready mentioned formation of the conductive bump 8. Thereby, a wiringboard material 71 having the conductive bumps 9 is formed.

At the same time, as shown in FIG. 5A and FIG. 5B, a metal foil 1 to bethe third wiring layer is prepared, and at necessary positions on thesingle side thereof (positions according to a layout as a particularfour-layered wiring board) the conductive bumps 9 are formed. Theformation of the conductive bumps 9 is performed also similarly to theabove. Thereby, a metal foil 11 having the conductive bumps 9 is formed.

FIG. 6 includes diagrams showing a process for fabricating afour-layered wiring board by use of the wiring board material 71fabricated by the process shown in FIG. 4A and FIG. 4B and the metalfoil 11 shown in FIG. 5A and FIG. 5B as materials. FIG. 7 includesperspective views showing the process shown in FIG. 6. In FIG. 6 andFIG. 7, the already explained regions are given the same referencenumerals.

As shown in FIG. 6 upper side and FIG. 7 upper side, respectively,first, the metal foil 1 is disposed through a prepreg to be aninsulating board 51 so as to face a surface on which the conductivebumps 9 are formed of the wiring board material 71, and a side on whichthe conductive bumps 9 are formed of the metal foil 11 is disposedthrough the prepreg to be the insulating board 51 so as to face asurface on which a conductive bump 9 is not formed of the wiring boardmaterial 71. The prepreg to be the insulating board 51 may be onesimilar to the above-mentioned prepreg to be the insulating board 5.

Next, as shown in FIG. 6 center and FIG. 7 center, a four-layered wiringboard 21 is obtained by stacking, pressurizing and heating five, thatis, the metal foil 1, insulating board 51, wiring board material 71,insulating board 51, and metal foil 11, and thereby integrating these.In the double-sided wiring board 21, each of the wiring patterns 1 a onboth sides of the wiring board material 71 is integrated so as to sinkin a thickness direction of the insulating boards 51, and the conductivebumps 9 penetrate through the each of the insulating boards 51 and comeinto an electrical contact with the opposing metal foil 1 or the pattern1 a. Such a state is realized because the insulating boards 51 hadthermo-plasticity and thermo-setting properties, and the conductivebumps 9 are originally formed in substantial cone.

In the four-layered wiring board 21, since an electrical continuitybetween an outer wiring layer and an inner wiring layer is establishedby means of the conductive bumps 9, there is no need of performing afurther process such as through-hole formation for establishing anelectrical continuity between these. Accordingly, since a space for usein through-hole formation is not necessary, a higher densityfour-layered wiring board may be obtained. In addition, in view of notadversely affecting on the layout of the other layers, needlessness ofthe through-hole formation is more significant as the number of wiringlayers increase.

Next, as shown in FIG. 6 lower side and FIG. 7 lower side, the metalfoils 1 on both sides of the four-layered wiring board 21 are patternedinto a pattern 1 b necessary as a wiring board. Due to the patterning, afour-layered wiring board 22 is formed. In the patterning, as mentionedabove, existing methods may be used, and due to the patterning avortically shaped inductor may be formed.

Furthermore, although the processes following the above are not shown bymeans of the drawings, the formation of solder resist and plating layersincluding on the pattern 1 b, mounting of surface-mounting components onthe pattern 1 b, or flip-chip mounting of semiconductor chips may beimplemented according to existing methods.

In the above-explained embodiments, an explanation is given for a casewhere a four-layered wiring board is fabricated with the double-sidedwiring board 7 a (7) obtained according to the fabricating method thatis explained in FIG. 1A and FIG. 1B, or FIG. 2A and FIG. 2B as a corewiring board. Accordingly, the four-layered wiring board may befabricated while maintaining features as the already-explaineddouble-sided wiring board 7 a (7). In addition, since the insulatingboard 51 that is an organic material is used when forming into amulti-layered structure, the formed multi-layered wiring board may bemade lighter than ceramic one.

In the above explanation, a four-layered wiring board is fabricated byuse of the double-sided wiring board 7 a (7). A three-layered wiringboard may be substantially similarly fabricated. That is, as one method,in FIG. 6 upper side, when three from the top (three of metal foil 1,insulating board 51 and wiring board material 71) is stacked,pressurized and heated and thereby these are integrated, a three-layeredwiring board is obtained. Furthermore, as another method, in FIG. 6upper side one, by stacking, pressurizing and heating three from thebottom (since in this case, the conductive bump 9 on the wiring boardmaterial 71 is unnecessary, the three is the wiring board material 7 a(7), insulating board 51 and metal foil 11), and thereby integratingthese, a three-layered wiring board is obtained.

Even in such a three-layered wiring board, a three-layered wiring boardmay be realized while maintaining features as the above-explaineddouble-sided wiring board 7 a (7).

Furthermore, in the above explanation, cases where passive elements arenot previously incorporated in the third and fourth wiring layers of thefour-layered wiring board and in the third wiring layer of thethree-layered wiring board are explained. However, in FIG. 6 upper sideone, by use of the coated/formed metal foil 4 (the formation surface ofthe passive element is used directed downward) shown in FIG. 1A or FIG.2A in place of the upper side metal foil 1, and by use of the conductivebump formed metal foil 4 a shown in FIG. 2A in place of the metal foil11, passive elements may be incorporated in the third and fourth wiringlayers.

According to these, the four-layered wiring board 22 may be formed inthe shape where the third and fourth wiring layers of the four-layeredwiring board 22 are previously provided with the resistor due to theresistive element 3 and the capacitor due to the dielectrics 2. Sincethe resistors and capacitors with which the third and fourth wiringlayers are provided are also previously formed on the metal foil 1before the stacking, there are the advantages similar to the resistorand the capacitor with which the first and second wiring layers areprovided. Furthermore, the resistors with which the third and fourthwiring layers are provided may be also trimmed by use of the pattern 1b. In addition, by previously coating a vortical conductive paste on themetal foil 1, the inductor due to the conductive paste may be formed onthe third and fourth wiring layers.

Furthermore, when the above-explained method is repeated and used, awiring board having wiring layers exceeding four layers may be easilyformed. When, for instance, a six-layered wiring board is fabricated, inFIG. 6 upper side one, in place of the wiring board material 71, one inwhich the conductive bumps are formed on a single side of theflour-layered wiring board 22 may be utilized. According to suchrepetition, furthermore multi-layered wiring boards are obtained.

FIG. 8 is a perspective view showing an example of the four-layeredwiring board fabricated according to the fabricating method shown inFIG. 6 and FIG. 7. In the four-layered wiring board 22 a in thisexample, by use of the pattern 1 b of the outer wiring layer, a land formounting a semiconductor device 32 and surface-mount components isformed, and a loop antenna 31 is formed near an outer periphery of thefour-layered wiring board 22 a.

Thereby, the semiconductor device 32, the loop antenna 31 and thepassive elements (ones that are incorporated in the wiring board andsurface-mounted components) necessary for, for example, an IC card(integrated circuit card) that delivers information via radio areintegrated and formed into a four-layered wiring board. The formation ofthe loop antenna 31 by use of such the pattern may be performed by useof the pattern 1 a on the double-sided wiring board 7 (7 a) alreadydescribed in FIG. 1B or FIG. 2B.

FIG. 9 is a partial sectional view as an example of the double-sidedwiring board fabricated according to the fabricating method according tostill another embodiment of the present invention. Constituent elementsthat are already explained are given the same reference numerals.

This double-sided wiring board 7 b is different from one shown in FIG.2B in that as a lead wire of the resistive element 3, a conductive bump8 that penetrates through the insulating board 5 is in direct use. Inorder to fabricate a double-sided wiring board in such a configuration,when the metal foil 4 a shown in FIG. 2A is formed, the position of theconductive bump 8 need only be set so that it may be formed on theresistive element 3 of the metal foil 1.

Then, as shown in FIG. 2B, these are laminated and followed bypatterning the metal foils 1 on both sides. In the patterning, the metalfoil 1 on a side in contact with the resistive element 3 is patterned sothat the metal foil 1 may not completely come into contact with theresistive element 3.

In thus configured resistor, since a lead wire thereof is not a metalused in the metal foil 1, without considering compatibility with themetal a resistive paste to be the resistive element 3 may be selected.The compatibility shows difficulty with which chemical and physicalchanges occurs at interfaces of, for instance, the metal (for instance,copper) of the metal foil 1 and the resistive element 3 when these comeinto contact. Bad compatibility may cause earlier corrosion on any oneof these. In the present embodiment, since it is not necessary toconsider the compatibility at least with the metal foil 1, a range ofchoice of the resistive pastes may be further expanded. Accordingly,further higher precision may be accomplished.

FIG. 10 is a bottom view as an example of the double-sided wiring board7 b shown in FIG. 9. The regions corresponding to FIG. 9 are given thesame reference numerals.

As shown in FIG. 10, the contact between the resistive element 3 and theconductive bump 8 may occur at a plurality of points (three in this caseshown in the figure) at one end. This is because while a shape of theresistive element 3 is varied in length and breadth according to anecessary resistance value, the size of the conductive bump 8 isnormally fixed due to the simultaneous formation by use of, forinstance, printing. By use of a plurality number of the conductive bumps8, the lead wires may be drawn out corresponding to the size of theresistive element 3.

FIG. 11 is a partial sectional view showing another example to oneexample shown in FIG. 9. The constituent elements that are alreadyexplained are given the same reference numerals.

The double-sided wiring board 7 c is similar to one shown in FIG. 9 inthat the conductive bumps 8 a that penetrate through the insulatingboard 5 is directly formed on the resistive element 3. However, in thecase shown in FIG. 11, the conductive bumps 8 a are used, not as thelead wire, as heat conductor to the resistive element 3. The conductivebump 8 a works as a heat conductive bridge with the wiring pattern 1 con a rear surface side of the resistive element 3. One resistive element3 may be provided with a plurality of the conductive bumps 8 a.

In a resistor that is configured so as to have the conductive bumps 8 afor heat conduction, Joule heat that is generated due to the resistormay be efficiently dissipated from both surfaces of the wiring board byuse of the conductive bumps 8 a and the wiring pattern 1 c as heat-sink.Accordingly, since the resistor is increased in its power rating,thereby a degree of freedom in circuit designing applied for the wiringboard may be advantageously improved.

FIG. 12A and FIG. 12B are partial sectional views for explaining oneexample of a double-sided wiring board fabricated according to thefabricating method according to still another embodiment of the presentinvention. FIG. 12A shows an intermediate stage to a state shown in FIG.12B. Furthermore, the constituent elements that are already explainedare provided with the same reference numerals.

The double-sided wiring board 7 d is different from one shown in FIG. 1Aand FIG. 1B in that the pattern 1 a and an electrical conductor 35formed from the conductive paste are used as both end electrodes of thedielectrics 2.

In order to fabricate a double-sided wiring board in such aconfiguration, first, as shown in FIG. 12A, after dielectrics 2 iscoated/formed on a metal foil 1, a conductive paste to be an electricalconductor 35 is coated including on the dielectrics 2 and extending ontothe metal foil 1. In the coating, a method identical to that used in thecoating of the dielectric paste to be the dielectrics 2 may be utilized.Treatment such as predetermined drying and so on is applied to thecoated conductive paste. Then, the metal foil 1 is used in place of thecoated/formed metal foil 4 shown in FIG. 1B upper side or FIG. 2B upperside and laminated. By further patterning the metal foils 1 on bothsides, the double-sided wiring board 7 d as shown in FIG. 12B may beobtained (in a strict sense, since there are the conductive bumps 8 inFIG. 12B, it shows a case applied to the case shown in FIG. 2B. However,the conductive bump 8 is not indispensable).

In a structure around the dielectrics 2 like this, since the pattern 1 aand the electrical conductor 35 sandwich the dielectrics 2 and form aso-called parallel plate capacitor, a capacitor having highercapacitance may be formed. Furthermore, all of the already explainedimprovement effect as the passive element and wiring board ismaintained.

FIG. 13A and FIG. 13B are partial sectional views for explaining anotherexample to one example shown in FIG. 12A and FIG. 12B. FIG. 13A shows anintermediate stage to a state shown in FIG. 13B. Furthermore, theconstituent elements that are already explained are provided with thesame reference numerals.

The double-sided wiring board 7 e is one in which the aforementionedparallel plate capacitor structure is further actively formed. Due tothe lamination like this, a capacitor having higher capacitance may beformed.

Specifically, as shown in FIG. 13A, first, dielectrics 26 iscoated/formed on a metal foil 1 followed by coating a conductive pasteto be an electrical conductor 36 so as to include on the dielectrics 26and extend onto the metal foil 1. After the coating, processes such aspredetermined drying and so on are performed. Next, a dielectric pasteto be the dielectrics 27 is coated so as to include on the electricalconductor 36 and come into contact with the dielectrics 26. After thecoating, processes such as predetermined drying and so on are performed.Next, the conductive paste to be an electrical conductor 38 is coated soas to include on the dielectrics 27, not to come into contact with theelectrical conductor 36, and to extend onto the metal foil 1. After thecoating, processes such as predetermined drying and so on are performed.

Furthermore, the dielectric paste to be dielectrics 28 is coated so asto include on the electrical conductor 38 and come into contact with thedielectric 27. After the coating, processes such as predetermined dryingand so on are performed. Next, a conductive paste to be an electricalconductor 37 is coated so as to include on the dielectrics 28, not tocome into contact with the electrical conductor 38, and to come intocontact with the electrical conductor 36. After the coating, processessuch as predetermined drying and so on are performed. The coating of thedielectric paste to be individual dielectrics 26, 27 and 28, and thecoating of the conductive paste to be individual electrical conductors36, 37 and 38 are performed similarly to the cases of the dielectrics 2and the electrical conductor 35 in the embodiment shown in, forinstance, FIG. 12A and FIG. 12B.

Then, the metal foil 1 is used in place of the coated/formed metal foil4 shown in FIG. 1B upper side or FIG. 2B upper side and is laminated.Furthermore, by patterning the metal foils 1 on both sides, adouble-sided wiring board 7 e as shown in FIG. 13B may be obtained(since there are the conductive bumps 8 in FIG. 13B, in a strict sense,it shows a case applied to the case shown in FIG. 2B. However, theconductive bumps 8 are not indispensable). The patterning of the metalfoil 1 is performed so that as one electrode a pattern that occupiesalmost on the dielectrics 26 and comes into contact also with theelectrical conductor 38 may exist, and as another electrode a patternhaving an electrical continuity with electrical conductors 36 and 37 mayexist.

A capacitor due to such lamination may enable to realize a furtherhigher capacitance by further performing similar lamination.Furthermore, all of the aforementioned improvement effect as the passiveelement and the wiring board is maintained.

Although the above-explained examples due to FIGS. 9 through 13B are ofthe cases of the double-sided wiring board, it is obvious that outerwiring layers in the four-layered wiring boards (or the above-explainedthree-layered wiring boards) as shown in FIG. 6 and FIG. 7 may allow toform the above-explained passive elements. Furthermore, the situationsare identical also in the case of a multi-layered, exceeding fourlayers, wiring board.

FIG. 15A and FIG. 15B are diagrams for explaining one example of afour-layered wiring board fabricated according to the fabricating methodaccording to still another embodiment of the present invention. FIG. 15Ais a sectional view and FIG. 15B is a top view thereof. Theaforementioned constituent numerals are given the same referencenumerals.

The four-layered wiring board is different from one shown in FIG. 6 andFIG. 7 in that there are formed magnetically permeable bumps 8A and 9Athat, respectively, penetrate through insulating boards 5 and 51 andthese magnetically permeable bumps 8A and 9A are in contact in apenetrating direction. Furthermore, patterns 1 a and 1 b are patterned,respectively, as shown in FIG. 15B, so as to surround the magneticallypermeable bumps 8A and 9A and, as shown in FIG. 15A, the conductivebumps 8 and 9 bring ambient patterns into an electrical continuity in avertical direction.

That is, the magnetically permeable bumps 8A and 9A work as a core of aninductor, and each patterns 1 a and 1 b work as a helical inductor coilas a whole. In thus structured inductor, since the magneticallypermeable material is used as a core and a coil is realized as a helicalcoil around the core, an inductance value may be increased. It isobvious that the inductor due to such a core and helical structure is,without restricting to such the four-layered wiring board, may beconfigured similarly even in a double-sided wiring board, three-layeredwiring board and multi-layered, exceeding four layers, wiring board.

In order to fabricate such the inductor that is incorporated in afour-layered wiring board, first, when a double-sided wiring board as acore wiring board is fabricated, in place of the coated/formed metalfoil 4 in FIG. 2B upper side, a magnetically permeable bump formed metalfoil fabricated according to the similar knack as the conductive bumpformed metal foil 4 a is used.

A magnetically permeable bump 8A may be formed on a place necessary as awiring board on the coated/formed metal foil 4 by means of, forinstance, screen printing. For this, as a magnetically permeable paste,for instance, one in which magnetically permeable material powder (forinstance, ferrite powder) is dispersed in a paste-like resin followed bymingling a volatile solvent is prepared, and this is coated by means ofscreen-printing on the metal foil 4. The magnetically permeable bump 8Ais necessary to have a height enough to penetrate through the insulatingboard 5. Accordingly, when one time screen-printing cannot give anecessary height, screen-printing is repeated a plurality of times toadd height in a height direction while disposing a drying processbetween the screen-printings, and thereby forming into a substantiallyconical shape as a whole.

Then, following the above, processes up to one shown in FIG. 2B lowerside are implemented. According to the processes up to this one, first,in the double-sided wiring board, an inductor due to a helical structuremay be obtained.

Furthermore, in fabricating in a four-layered wiring board, in place ofthe metal foil 1 in FIG. 6 upper side, a metal foil provided with themagnetically permeable bump 9A thereon is used (a surface on which themagnetically permeable bump 9A is formed is directed downward). Inaddition, in place of the wiring board material 71 in FIG. 6 upper side,one in which the conductive bump 9 is formed on one side (top surface inthe figure) of the double-sided wiring board including theaforementioned magnetically permeable bump 8A, and the magneticallypermeable bump 9A is formed on the other surface is used. Themagnetically permeable bump 9A can be formed similarly to the above.

Thereafter, the processes up to one shown in FIG. 6B lower side areperformed. Thereby, an inductor due to a helical structure in which alllayers of a four-layered wiring layer are used as coil can be obtained.Furthermore, by performing similarly, an inductor due to a helicalstructure in which all layers of an N-layered wiring layer are used ascoil can be obtained.

FIG. 16A and FIG. 16B are diagrams for explaining another example to oneexample shown in FIG. 15A and FIG. 15B. FIG. 16A is a sectional viewthereof and FIG. 16B is a top view thereof. The aforementionedconstituent elements are given the same reference numerals.

This four-layered wiring board is different from one shown in FIG. 15Aand FIG. 15B in that a magnetically permeable pillared body 82 thatpenetrates through the insulating boards 5 and 51 is used in place ofthe magnetically permeable bumps 8A and 9A of the four-layered wiringboard shown in FIG. 15A and FIG. 15B.

In this case too, the magnetically permeable pillared body 82 works as acore of an inductor, and each patterns 1 a and 1 b work as a helicalinductor coil as a whole. Accordingly, similarly to the above, aninductance value may be increased. It is obvious that an inductor due tosuch a core of the magnetically permeable pillared body 82 and a helicalstructure, without restricting to such a four-layered wiring board, maybe configured similarly even in a double-sided wiring board,three-layered wiring board, and multi-layered, exceeding four layers,wiring board.

In order to fabricate such an inductor incorporated in four-layeredwiring board, a four-layered wiring board that has undergone the processshown in FIG. 6 lower side may be provided with a through-hole 81, andthe formed through-hole 81 may be filled in with a magneticallypermeable material. Similarly, a multi-layered, exceeding four layers,wiring board also, after a multi-layered wiring board having finallyneeded layers has been formed, may be provided with a through-hole, andthe formed through-hole may be filled in with a magnetically permeablematerial. As a magnetically permeable material, the magneticallypermeable material as mentioned above may be used, or previouslysolidified magnetically permeable pillared body may be inserted andfixed.

The present invention has been described with reference to certainpreferred embodiments, but it will be understood that variations andmodifications can be made within the spirit and scope of the invention.

1. A wiring board provided with a passive element comprising: aninsulating board having a first surface and a second surface; first andsecond wiring layers, respectively, disposed on the first surface andthe second surface of the insulating board; a conductive bump thatpenetrates through the insulating board and is in an electricalconnection with the first wiring layer and the second wiring layer; anda magnetically permeable bump that penetrates through the insulatingboard; wherein the first wiring layer has a first pattern that surroundsthe magnetically permeable bump; the second wiring layer has a secondpattern that surrounds the magnetically permeable bump; and the firstand second patterns are in continuity due to the conductive bump,wherein the wiring board further comprises a second insulating boarddisposed on the first wiring layer side of the insulating board, a thirdinsulating board disposed on the second wiring layer side of theinsulating board, a third wiring layer disposed on a surface sidedifferent from the insulating board of the second insulating board, afourth wiring layer disposed on a surface side different from theinsulating board of the third insulating board, a second conductive bumpthat penetrates through the second insulating board and is brought intoelectrical connections with the first wiring layer and the third wiringlayer, a second magnetically permeable bump that penetrates through thesecond insulating board, a third conductive bump that penetrates throughthe third insulating board and is brought into electrical connectionswith the second wiring layer and the fourth wiring layer, and a thirdmagnetically permeable bump that penetrates through the third insulatingboard; wherein the first wiring layer is disposed so as to sink in athickness direction of the second insulating board, the second wiringlayer is disposed so as to sink in a thickness direction of the thirdinsulating board, the magnetically permeable bump, the secondmagnetically permeable bump, and the third magnetically permeable bumpare disposed in series, the third wiring layer has a third pattern thatsurrounds the second magnetically permeable bump, the fourth wiringlayer has a fourth pattern that surrounds the third magneticallypermeable bump, the first and third patterns are in an electricalcontinuity due to the second conductive bump, and the second and fourthpatterns are in an electrical continuity due to the third conductivebump.
 2. A wiring board provided with a passive element as set forth inclaim 1, comprising: a pillared body that has a magnetically permeablematerial and penetrates through the insulating board, the secondinsulating board, and the third insulating board in place of themagnetically permeable bump, the second magnetically permeable bump, andthe third magnetically permeable bump.